By Bobby Magill
One of the study’s most important findings was that US Environmental Protection Agency greenhouse gas emissions inventories for methane emissions from livestock operations in 2004 were erroneous, while air samples measuring methane emissions from oil and gas fields showed that the EPA overestimated methane emissions from the oil and gas industry. “The EPA faces enormous challenges in compiling their GHG inventory,” Wecht said. “In many sectors, the EPA numbers compare favorably to the numbers in this study.
A European satellite slated for launch in 2015 will be able to do that and allow new high-resolution methane emissions data to be available once again, Wecht said. “I think one of the contributions of this paper is demonstrating our difficulty to allocate emissions to different sources,” Stefan Schwietzke, a researcher at the National Oceanic and Atmospheric Administration’s Earth Systems Laboratory who just published his own study on methane emissions from oil and fields, said via email. “Different techniques give us different results.
Greenhouse gas emissions studies are done in one of two ways: A “bottom up” approach measures methane emissions at their source and estimates overall emissions for an area based on that data. A “top down” approach measures methane emissions from above and estimates a region’s overall emissions based on actual measurements in the atmosphere. “We need a better understanding of why there is a gap between bottom-up and top-down in order to judge the accuracy of the inventories,” Schwietzke said.
The study also shows how satellites can be used to measure methane emissions in the future. “This study shows that 10 years ago, emissions from livestock were the single largest source of methane in the United States,” Harvard postdoctoral researcher Kevin Wecht, the study’s lead author, said.
But Wecht said that methane emissions have accounted for roughly half the warming as CO2 emissions since the industrial revolution, and slashing methane emissions now could buy humanity time to figure out how to more effectively cut CO2 emissions. “CO2 will require huge changes in energy infrastructure in the way we use coal, oil and natural gas,” Wecht said, adding that if more accurate measurements of methane emissions can be taken, scientists may be able to find ways to slash methane emissions that are less expensive than cutting CO2.
Data from the satellite helped Harvard University researchers determine that livestock emitted more methane than oil and gas did in 2004, according to a new study – the first to use high-resolution satellite data to study methane emissions in the US.
Enteric fermentation from livestock ranks second, and landfill gas emissions ranks third. “While CO2 is the big gorilla in the room, methane itself contributes significantly to global warming,” Wecht said. “Acting quickly on methane emissions may be able to keep the planet cooler (in the short term) while we invest in longer-term reductions in CO2 emissions.
I am not an expert on satellite data, but it is encouraging to see that the satellite data is consistent with some local air measurements in the US,” Schwietzke said. “It is also consistent with my global methane work suggesting that bottom-up agriculture/waste methane emissions may be underestimated.
Wecht’s team used satellite data from 2004 because the satellite that measured methane emissions went out of service two years ago, and the quality of data from the satellite began degrading in 2005.
Methane emissions from livestock production in the US were 40 per cent higher than federal government estimates and 70 per cent higher than methane emissions from the oil and gas industry in 2004, according to the study.
Read more here: Business Spectator